1. The Field of the Invention
The present invention relates to vehicular safety. More specifically, the present invention relates to a novel apparatus and method for distributing inflation gases in a cushion for an inflatable curtain module.
2. The Relevant Technology
The inclusion of inflatable safety restraint devices, or airbags, is now a legal requirement for many new vehicles. Airbags are typically installed in the steering wheel and in the dashboard on the passenger side of a car. In the event of an accident, an accelerometer within the vehicle measures the abnormal deceleration and triggers the ignition of an explosive charge. Expanding gases from the charge fill the airbags, which immediately inflate in front of the driver and passenger to protect them from impact against the windshield. Side impact airbags, known as inflatable curtains, have also been developed in response to the need for similar protection from impacts in a lateral direction, or against the side of the vehicle.
However, despite their enormous lifesaving potential, the effectiveness of side impact airbags has been somewhat limited by the speed with which inflation gases are able to fill the cushion. Side impact cushions are often designed to unfold or unroll downward to inflate beside a person to keep the person from hitting the door or window during lateral impact. Since a vehicle occupant may be leaning forward, reclined in the seat, or at any position between, such cushions are often made somewhat long to ensure that the occupant hits the cushion.
Cushions for inflatable curtains are often inflated by an inflator positioned either fore or aft of the cushion. Consequently, unlike many front impact airbags, a long gas flow path exists between the inflator and the outermost extent of the cushion. The length of the gas flow path is problematic for a number of reasons.
One such reason is that the cushions are unable to inflate rapidly enough to provide optimal protection. Since most airbag systems are unable to detect a collision until impact has begun to occur, the airbag must move from an uninflated, stowed configuration to a fully inflated configuration within a small fraction of a second. The long flow path increases the time required by the inflation gases to traverse the cushion. Thus, the cushion may not obtain a fully inflated state before the vehicle occupant strikes the cushion.
In an attempt to compensate for the longer gas flow path, inflators with a higher xe2x80x9crise rate,xe2x80x9d or rate of pressure increase of expelled gases, and a higher volume of expelled gases, have been used. Unfortunately, when the inflation gases are more highly pressurized, there is a higher danger of damage to the cushion. Highly-pressurized gases produce stresses in the material of the cushion that may tend to rip the cushion material or split the cushion open along the seams, thereby jeopardizing the effectiveness of the cushion.
Furthermore, even when the inflator produces a larger amount of gas, the inflation gas may expand in the portion of the cushion nearest to the inflator, rather than continuing toward the furthest extents of the cushion. As a result, the cushion may not be uniformly inflated in time to shield occupants properly from impact.
Existing airbag configurations developed in an attempt to solve this problem also have some drawbacks. Some are difficult and/or expensive to manufacture, in part due to additional drilling, punching, aligning, fixturing and the like that must be carried out. Some increase the expense of airbag installation because they have parts that must be inserted into a finished cushion prior to installation of the cushion in a vehicle. Others require additional time to reach a steady state after inflation due to backflow and other continued motion of inflation gases within the cushion.
Accordingly, a need exists for an apparatus and method for distributing inflation gases in an inflatable cushion in a comparatively uniform and rapid manner. A need further exists for such an apparatus and method that can be carried out with a minimum of added expense to the manufacture and installation of the cushion. Furthermore, a need exists for such an apparatus and method that is capable of stabilizing the location of inflation gases when the cushion has been fully inflated.
The apparatus and method of the present invention have been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available airbag component attachment systems and methods. Thus, it is an overall purpose of the present invention to provide an apparatus and method for distributing inflation gas within an airbag cushion with a high degree of inflation speed and uniformity, manufacturing and installation economy, and inflation stability
An inflatable curtain module according to the present invention may have an inflatable cushion configured to activate to shield a vehicle occupant from impact against a lateral surface of the vehicle, such as a door or window. The cushion preferably has at least one protection zone, and may optionally have multiple protection zones, each of which may serve to protect one occupant. Thus, a single cushion may, for example, cover a rear door or surface as well as a front door, so that an occupant of a back seat can be protected as well as an occupant of a front seat. The protection zones may be connected by a connection zone configured to convey tension and inflation gas between the protection zones.
The cushion may have a first membrane and a second membrane, each of which has an interior portion and an outer edge substantially surrounding the interior portion. The first membrane may also have a mounting surface disposed within the interior portion of the first membrane, and running along a portion of the length of the interior portion. The first and second membranes may be attached at the outer edges such that the interior portions face each other to form the one or more protection zones of the cushion. Each protection zone may be divided into a number of chambers, which may, for example, be oriented substantially upright.
The membranes may be attached in a number of different ways, including sewing, RF welding, chemical or adhesive bonding, or the like. The chambers maybe separated from each other through the use of a similar method, or through the use of an entirely different attachment process.
An inflation channel may be disposed along a portion of the length of the cushion, and may be attached to the mounting surface of the first membrane such that the inflation channel is affixed within one or more protection zones of the cushion. The inflation channel may be coupled to receive inflation gas from an inflator by, for example, connecting a gas guide to the inflator and to the inflation channel. The inflation channel may have a plurality of holes disposed along its length, for distributing inflation gases throughout the cushion.
The inflation channel may have a conduit shaped to convey inflation gas. Additionally, the inflation channel may have a mounting flap configured to be affixed to the mounting surface of the first membrane. The inflation channel may operate to receive and dissipate the initial shock of the expanding, heated inflation gas, thereby preventing damage to the membranes of the cushion. Furthermore, the inflation channel may be designed such that inflation gases are able to freely exit the inflation channel through the holes, but are unable to re-enter as freely.
For example, a gas outlet extension may run along the length of the conduit; the gas outlet may have a substantially tapered shape with an enlarged end toward the conduit and a narrow end away from the conduit. The holes may be formed in the narrow end. Consequently, when the pressure within the conduit is greater than the pressure outside the conduit, the enlarged end remains open and in fluid communication with the conduit. However, when the pressure outside the conduit becomes larger than that within the conduit, the gas outlet extension is compressed to close the holes and limit fluid communication between the conduit and the gas outlet extension. Consequently, backflow of inflation gases into the inflation channel may be limited, and the pressure within the cushion may therefore be comparatively stable directly after inflation.
Attachment of the mounting flap to the mounting surface maybe carried out through any of the attachment methods mentioned above. In order to attach the mounting flap through RF welding, the inflation channel may be constructed of a urethane-based material, or may be constructed of a fabric and coated with urethane at the mounting flap. The mounting surface may similarly be coated with a urethane-based material so that the mounting flap can be RF welded to the mounting surface.
The holes may be strategically positioned and sized to control the flow of inflation gases into each portion of the cushion. More specifically, the holes may be sized or spaced apart in a variable fashion so that the cushion inflates substantially uniformly along its length. For example, the holes may be made comparatively smaller toward the point of entry of inflation gas, and may become larger further into the cushion. Thus, gas flow into the portions of the cushion nearest to the inflator is limited by the flow restriction imposed by the smaller holes. Flow into the portions further from the inflator is less restricted to compensate for the fact that inflation gases must travel a greater distance to reach those portions of the cushion.
Alternatively, the holes maybe spaced apart in a variable fashion, so that the holes are comparatively far apart close to the point of entry of the inflation gas, and comparatively close together further from the point of entry. The holes may then be of a uniform size. The existence of a larger number of holes decreases the flow restriction imposed on inflation gases moving into the portions of the cushion that are further from the point of entry.
The inflation channel may be easily manufactured in a number of ways. For example, the inflation channel maybe extruded from a urethane-based material in the desired shape. The gas outlet extension may be formed fully closed, and selectively opened to provide the holes. In the alternative, the inflation channel may be formed form a workpiece with a slit along the length of the workpiece. Sections of the slit may be selected for use as holes; the slit may then be closed by attaching attachment surfaces of the slit exclusively between the selected sections. The inflation channel may also be formed from a fabric, using conventional fabric shaping and/or attachment methods.
Through the system and method of the present invention, a cushion may receive a more uniform airflow, directed comparatively evenly into all parts of the cushion. Furthermore, inflation stress may be absorbed without risking damage to the cushion. Yet further, continued motion of inflation gases after the cushion has been filled may be restricted through the use of a backflow preventative inflation channel shape. Yet further, such benefits, and more besides, may be obtained without adding greatly to the overall manufacturing or installation cost for the inflatable curtain module.
These and other objects, features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or maybe learned by the practice of the invention as set forth hereinafter.